This invention relates generally to railway coupler arrangements and more particularly to an improved slackless drawbar arrangement whereby the yoke, follower and draft gear in a standard coupler can be removed from a center sill and retrofitted with a short yoke drawbar connection thereby converting a railway coupling arrangement from coupler to drawbar and vice versa, without modifying the standard center sill.
Railway cars are connected together by coupler members, namely drawbars or couplers. Drawbars are integral units known to be used in the railroad industry to extend between and semipermanently connect two or more cars. Couplers are independent units in each car which interconnect with one another between adjacent cars to form a connection. In either arrangement, a shank and butt end of the drawbar or coupler extends into the center sill of a railway car where it is secured to transmit longitudinal loads to the car.
This invention is directed to an improvement in the center sill construction for conversion from standard coupler arrangements to slackless drawbar arrangements without modifying the center sill construction. By slackless, it is meant that the drawbar is received within the center sill in a manner to minimize longitudinal play or movement. However, because successive railway cars in a train must accommodate relative movement between cars when curves and inclines are negotiated, there must be provision for each car to move in pitch, yaw and roll modes with respect to the coupler member. Moreover, there must be a provision to remove the drawbar components for repair and or retrofitting an approved standard center sill to accept change out to a standard AAR-type coupling system, or vice versa.
In a slackless drawbar arrangement, the drawbar member is held in a way to eliminate or minimize longitudinal movement with respect to the car body. The slackless arrangement is usually accomplished by providing a tapered wedge between a rear wall of a pocket casting (secured in the center sill) and a follower block, which rests against the butt end of the drawbar member. The pocket casting rear outside wall bearing surface, in turn, abuts a set of center sill side wall rear stops for the purpose of indirectly transferring buff loads, while the drawbar pin typically transfers draft loads into the center sill side wall front stops. During draft loading, the wedge tends to move downward by gravity, maintaining a slack free system whereby the downward weight of the wedge forces the follower block away from the pocket casting end wall, firmly against the butt end of the coupler shank; all loads are then transferred through the coupler pin into the front stops. When cars are being pushed, the buff loads force compression of the coupler member against the follower, wedge, and pocket end wall, transferring the loads through these members into the rear stops. Examples of slackless drawbar systems are shown in Altherr et al., U.S. Pat. No. 4,700,853 and in Altherr et al, U.S. Pat. No. 4,456,133.
One problem with the slackless arrangements is that the front and rear center sill stops of the coupling system are rigidly secured, usually by welding, to the inside of the center sill. This results with a car being limited to strictly one type of coupler arrangement unless considerable time and expense is spent in removing the front stops when preparing the center sill for changeout to a standard coupler arrangement. It is advantageous in operating a railroad to have railway cars which can be converted from a standard coupler arrangement to a slackless drawbar arrangement without expensive modifications. Furthermore, it is desirable to have a drawbar retention arrangement which is removable yet utilizes the existing center sill front and rear stops so that distribution of buff and draft forces can be transferred more thoroughly throughout the center sill without sacrificing coupler angling performance.